This invention relates to systems for determining physical properties of a particulate bed such as a catalyst bed. More particularly, this invention relates to systems for determining load bearing and packing characteristics of fixed particulate beds such as those used in fixed bed reactors.
Efforts to determine packing properties or characteristics of catalysts have in the prior art often utilized systems which contained the catalyst in a rigid container. For example, one prior art approach has been to place a catalyst bed to be tested within a rigid cylinder, and then to apply forces to the upper surface of the catalyst bed by means of a piston which slides in the cylinder. An important drawback of this approach is that forces applied to the upper surface of the bed are not distributed uniformly throughout the bed. Instead, pressures in the bed are quite high near the piston, but decrease rapidly and non-uniformly with increasing distance from the piston.
Furthermore, many prior art efforts to determine crush properties of catalysts have been directed to measuring isolated physical characteristics such as crush strength and packing density. What really is of concern, however, to a catalyst user is a combination of properties, including packing, crush strength, differential pressure drop across a loaded bed, and flow characteristics of fluids through a packed bed.
These properties are not totally independent of one another. Packing influences the distribution of shearing and crushing forces experienced by individual catalyst particles within a loaded reactor. These forces cause attrition which results in a redistribution of packing and the forces resulting therefrom. If a significant increase in pressure drop across a catalyst bed occurs, the effectiveness of the loaded reactor to carry out catalyzed conversion processes can be decreased significantly. Crush strength of a catalyst can be important to whether a catalyst will pack in a commercially useful manner.
Since there has, up until now, been no single system of the type disclosed below capable of providing correlatable data between the physical properties of a particular catalyst and its ability to function in a loaded fixed bed, this invention fills a need not heretofore adequately satisfied. It is an object of this invention to provide a system, preferably a single apparatus, capable of providing correlatable data which can be used to predict the packing performance of a catalyst in a fixed bed reactor.